1. Field of the Invention
The present invention relates to a molding machine for molding detergent containers, cosmetic bottles or the like from parisons.
2. The Prior Arts
(A) Turntable driving system of a blow molding machine
For example, there is a rotary blow molding machine in which under an extruder for extruding a parison made of thermoplastic resin downward in the vertical direction, a turntable is arranged which has plural sets of shut-off molds mounted thereon, each set consisting of a pair of the shut-off molds for holding said parison therebetween and blow-molding the parison, and a driving gear for transmitting the rotation of a motor is intermeshed with an annular driven gear provided on the lower part of said turntable, thereby making the turntable intermittently rotatable, wherein hollow articles made of the resin are continuously molded (there is disclosed a similar structure thereto, for example in the official gazette of Japanese Patent Application Laid-open No. 256,420/1988).
In such a conventional rotary blow molding machine in which the driving gear for transmitting the rotation of a motor is directly intermeshed with the annular driven gear of a turntable, however, there is a drawback that the position of said turntable in its intermittent rotation or stoppage can not be positioned with high accuracy due to any backlash of both the gears.
Thus, the present invention is intended to provide a rotary blow molding machine in which the aforementioned problems can be solved.
(B) Parison extruding system of a blow molding machine
For example, there is a rotary blow molding machine in which under an extruder for extruding a parison made of thermoplastic resin downward in the vertical direction, a turntable is arranged which has plural sets of shut-off molds mounted thereon, each set consisting of a pair of the shut-off molds for holding said parison therebetween and blow-molding the parison, and the turntable is lifted up to the extruder side when said parison is fed into each pair of the shut-off molds, and it is lifted down to its original position after the feed of the parison, and said turntable is intermittently rotated by a motor equipped with a driving gear intermeshing with an annular driven gear provided on the turntable, wherein hollow articles made of the resin are continuously molded (there is disclosed a similar structure thereto, for example in the official gazette of Japanese Patent Application Laid-open No. 256,420/1988).
In such a conventional rotary blow molding machine in which a mold lifting mechanism for lifting up the turntable to the extruder side in the feed of a parison, other than a driving mechanism comprising a motor for rotating the turntable and the like, must be installed on the turntable side, however, there is a drawback that the structure of the molding machine on the turntable side is complicated and its weight becomes heavier.
Thus, the present invention is intended to provide a rotary blow molding machine in which the aforementioned problems can be solved.
(C) Extruder turning system of a blow molding machine
When a screw of the extruder for kneading thermoplastic resin is drawn out for cleaning, in the conventional rotary blow molding machine described in the item (A), the pair of said shut-off molds on the turntable and the screw to be drawn out of said extruder interfere with each other, and the turntable must be therefore moved, for instance along a pair of movement rails arranged in the installation place. As a result, there is required a wider installation space.
Thus, the present invention is intended to provide a rotary blow molding machine in which the aforementioned problems can be solved.
(D) Mold clamping unit of a blow molding machine
In the official gazette of Japanese Patent Application Laid-open No. 256,420/1988 aforesaid in the items (A), (B) and (C), there is disclosed a mold clamping unit for a rotary blow molding machine in which parisons made of thermoplastic resin are continuously molded to hollow articles made of the resin by a pair of shut-off molds.
The mold clamping unit of this rotary blow molding machine comprises roughly a bed plate, a pair of guide shafts fixed so as to be parallel on said bed plate by way of a supporting block, a pair of movable plates slidably provided on the pair of said guide shafts, in which said molds are fixed on their opposite surfaces, respectively, a pair of clamp rods fixed at their one end on the back surface side of each movable plate, which contact the respective molds with each other or alienate them from each other, a swing lever swingably supported on a bracket erected at one end of said bed plate by way of a pivot positioned almost at the same height as that of each guide shaft, in which the other end of one clamp rod is pivotally supported at its upper end, and its lower end part is protruded downward from the top surface of said bed plate, a slide rod slidably supported under the bed plate, in which one end thereof is pivotally supported at the other end of the one clamp rod of said swing lever, and a connection plate for connecting the respective other ends of said slide rod and the other clamp rod with each other. After the parison is fed from the extruder, the turntable having each pair of shut-off molds mounted thereon, which are clamped by said mold clamping unit, is intermittently rotated by the motor, wherein hollow articles made of the resin are continuously molded.
In the mold clamping unit of the conventional rotary blow molding machine mentioned above, in which the pivot of the swing lever of the mold clamping unit is positioned at the height of a pair of guide shafts and the pair of said guide shafts are provided nearly midway between the clamp rod and the slide rod, however, there is a drawback that the clamping force of the mold clamping unit can not be divided uniformly by the pair of said guide shafts and the bed plate, with any unnatural load applied on the bed plate. Furthermore, there is required a complicated retaining means in order to retain the opened or shut state of the pair of said molds.
Thus, the present invention is intended to provide a rotary blow molding machine in which the aforementioned problems can be solved.
(E) Parison cutting unit of a blow molding machine
For example, there is a parison cutting unit of a blow molding machine in which a cutter reciprocated by an air cylinder is provided on an extruder for extruding a parison made of thermoplastic resin downward in the vertical direction, and said cutter is repeatedly moved alternately forward and backward, thereby cutting in order the parison extruded from the extruder into a pair of shut-off molds arranged under said extruder, wherein hollow articles made of the resin are continuously molded.
In the parison cutting unit of such a conventional blow molding machine, in which the cutter is reciprocated by the air cylinder, thereby cutting the parison in order, and the cutting start-up positions in the forward and backward movements of said cutter are different, respectively, however, there is a drawback that each parison can not be cut at the same length at all times.
Thus, the present invention is intended to provide a parison cutting unit of a rotary blow molding machine in which the aforementioned problems can be solved.
(F) Flash shape correcting unit of a blow molding machine, and (G) Molding taking-out unit of a blow molding machine
In the official gazette of Japanese Patent Application Laid-open No. 111,167/1975, for example, there is disclosed a rotary blow molding machine in which hollow articles made of thermoplastic resin are continuously molded by use of parisons made of the resin. This rotary blow molding machine has a pair of rotary frames, and has, between the pair of said rotary frames, plural (eight) sets of shut-off molds, each set consisting of a pair of the shut-off molds which are opened or shut by a mold clamping unit. By an extruder positioned above the pair of said rotary frames, a parison is fed in order into each pair of said shut-off molds positioned under said extruder, and after the molds are clamped, said parison is cut off from the extruder by the rotation of the pair of said rotary frames in a given direction, and after the blow molding is carried out, a blow molding is taken out of the pair of said shut-off molds which are opened, by holding a flash of said blow molding by the chuck of a product taking-out unit.
In the conventional rotary blow molding machine mentioned above, which is composed so that the parison fed into the pair of said shut-off molds is cut off from the extruder when the pair of said rotary frames are rotated, however, there is a drawback that the upper end portion of the parison protruded upward from the top surface of the pair of said shut-off molds that will become a flash is easy to fold and bend to the top surface side of the pair of said shut-off molds shut, and said portion becomes a flash of a blow molding after its solidification in this state, and it is therefore difficult to hold said flash and take out said blow molding with the chuck of the product taking-out unit.
Thus, the present invention is intended to provide a rotary blow molding machine in which the aforementioned problems can be solved.
(H) Parison presealing method and unit of a blow molding machine
In the official gazette of Japanese Patent Publication No. 34,777/1989, there is disclosed a blow molding machine composed so as to have an extruder for extruding and hanging down a parison, a presealing device for presealing one end part of said parison, a preblowing device for preblowing a blow gas into the presealed parison, a pair of molds for holding said parison therebetween and closing both end parts of the parison, and a blowing device for injecting the blow gas into the parison enclosed in the molds until the parison accords with the cavity of said molds.
The reason why said parison is previously imparted with a given expansion by presealing and preblowing the parison is that when the parison is held between the molds and a blow needle of the blowing device is punctured into the parison, a sufficient space is formed between two parison skins so that said blow needle punctures only one parison skin of the annular parison and it does not puncture two parison skins thereof. If the blow needle punctures the two parison skins, it is impossible to inject the blow gas between the two parison skins of the same parison.
In the prior art, however, the presealing device is provided on the upper end part of a pair of molds and said one end part of a parison is presealed in the upper part of the pair of said molds.
Accordingly in the prior art, there are the following problems (1) to (3).
(1) The presealing of a parison is carried out in the upper part of the molds, i.e. just under the extruder. Therefore, the parison undergoes a strong bending action just under the dies and core which are the outlet of said extruder by the presealing device, and as a result, some ring mark flaws caused by this strong bending are formed on the inside and outside surfaces of the parison. Thus, a lower flash to be cut at the lower end part of the parison becomes larger, reducing the yield.
(2) At the stage where a parison is presealed, the parison is only extruded at a short length corresponding to the lower end part of a molding. When the preblowing is carried out simultaneously with the presealing, only the portion of the parison corresponding to the lower end of a molding is expanded and as a result, it is impossible to impart to said parison an expansion due to the preblowing that is uniform in the whole of the parison. In the prior art, accordingly, the control of preblowing is complicated, for instance which comprises, after the lapse of the presealing, starting up the preblowing, with waiting such a time that the lower end part of the parison reaches the vicinity of the lower part of the molds.
(3) If the extrusion of a parison is not carried out with blowing air into the parison, after the parison is sealed in the upper part of the molds, the inside of the parison will be negative in pressure and a molding will be inferior. Also in a cace the preblowing is not positively carried out, there is therefore required a preblowing device (which may be an atmosphere release passage) in order to prevent the negative pressure state in the inside of the parison.
It is, therefore, an object of this invention to obtain a superior molding by presealing a parison, with no formation of any ring mark flaw or the like thereon, and blow-molding said parison while air is enclosed in the parison, and to enable to simplify the control of preblowing when the preblowing is carried out.
(I) Ejector-contained molds of a molding machine
A molding machine has hitherto an ejector provided therein such as a blow needle or ejector pin.
In the official gazette of Japanese Utility Model Application Laid-open No. 114,136/1989, there is disclosed a molding machine in which an ejector pin driving part is provided on a mold fixture plate side and an ejector pin is provided on a mold side.
In a conventional blow molding machine, in addition, a blow needle driving part and a blow needle are provided on the mold fixture plate side.
In the prior art in which an ejector pin driving part is provided on the mold fixture plate side and an ejector pin on mold side, respectively, however, it is necessary to carry out an attaching and detaching work for the ejector pin driving part and the ejector pin, when the molds are attached on or detached from the mold fixture plate. And, it is difficult to ensure the smooth motion of the ejector pin, because of the presence of a mechanical looseness and an error in assemblying position in a portion where the ejector pin driving part and the ejector pin are attached or detached.
In the prior art in which a blow needle driving part and a blow needle are provided on the mold fixture plate side, furthermore, it is necessary to carry out a work of inserting the blow needle on the mold fixture plate side into a blow needle guide hole on the mold side, when the molds are attached on or detached from the mold fixture plate. And, it is difficult to ensure the smooth motion of the blow needle, because of the presence of an error in assemblying position between the blow needle on the mold fixture plate side and the blow needle guide hole on the mold side.
It is, therefore, an object of this invention to eliminate the setting work of an ejector such as a blow needle or ejector pin when molds are attached on or detached from a mold fixture plate, whereby the exchanging workability of the molds can be made satisfactory and the smooth motion of said ejector can be ensured.
(J) Mold pipe line connecting structure of a molding machine
In the official gazette of Japanese Patent Publication No. 48,412/1990, there is disclosed, as the mold pipe line connecting structure of a molding machine, such a connecting structure that an inlet and an outlet for a temperature regulating flow passage are opened in a clamp provided on a mold fixture plate side so as to press and hold molds against said mold fixture plate, and an inlet and an outlet for the temperature regulating flow passage are opened also on the surface of said molds pressed down by said clamp, wherein when the molds are fastened and fixed on the mold fixture plate by the clamp, both the inlets and outlets are communicated with each other in such a state that a sealing material is held under pressure between the mating surfaces of both said inlets and outlets.
According to this prior art, the pipe line on the mold fixture plate side and the pipe line on the mold side can be compactly connected at the same time when the molds are fixed onto the mold fixture plate.
In this prior art, however, there are the following problems (1) and (2).
(1) The exchanging workability of molds is inferior, because it is necessary to confirm that the inlet and outlet on the mold side accord with the inlet and outlet on the clamp side, when the clamp is fastened and fixed.
(2) Since a sealing material is held under pressure between the mating surfaces of the inlet and outlet on the mold side and the inlet and outlet on the clamp side, it is necessary to accompany a fastening and fixing means such as a bolt for each pair of these inlets and outlets. In a case the molds and clamp have plural pairs of pipe lines, the exchanging workability of the molds is inferior, because it takes a long working time.
It is, therefore, an object of this invention to simplify a pipe line connecting work when the pipe line on a mold fixture plate side and the pipe line on a mold side are compactly connected simultaneously with the fixing of the molds to the mold fixture plate, whereby the exchanging workability of the molds can be made satisfactory.
(K) Mold hanging structure of a molding machine
In the official gazette of Japanese Patent Application Laid-open No. 103,660/1986, there is disclosed a molding machine in which a hanger equipped with a device for moving and regulating a center of gravity is used to enable to hang up a pair of molds horizontally.
The official gazette of Japanese Utility Model Application Laid-open No. 34,214/1990 discloses a molding machine in which retainers provided in one pair of molds, respectively are retained with each other, thereby restraining the pair of said molds from opening when the molds are hung up.
In the prior art described in the official gazette of Japanese Patent Application Laid-open No. 103,660/1986, however, the molding machine becomes complicated in constitution, because a hanger must be equipped with a device for moving and regulating the center of gravity in order to enable to hang up a pair of molds horizontally.
In the prior art described in the official gazette of Utility Model Application Laid-open No. 34,214/1990, there is really no constitution for enabling to hang up a pair of molds horizontally, so that the molds may be inclined when they are hung up. Also in this prior art, the molding machine becomes complicated in constitution, because an especial retainer for restraining said molds from opening must be fixed on each of the molds in order to restrain the molds from opening.
It is, therefore, an object of this invention to enable to hang up a pair of molds horizontally by means of a simple constitution.
Furthermore, it is a further object of this invention to enable to restrain the molds from opening when they are hung up, by means of a simple constitution.